Antennas are used for various communication systems, such as television (TV), cellular phone, wireless data and local area network (LAN), personal communication service (PCS), etc., which are the rapidly developing areas. A clear and strong signal and wide coverage of sending and receiving information are very critical for the wireless communication systems. Therefore, good antennas are required.
Existing antennas in the market are proven to have various problems, such as narrow bandwidth, low gain, larger size and high cost. The narrow bandwidth particularly limits the range of applications. For example, if an antenna designed for person communication network (PCN) frequency band may not cover PCS frequency band. The low gain results in poor coverage in communication systems; vice-versa requiring high receiving sensitivity, or high transmission power. Most users prefer smaller size antenna to create open space. Lastly, the high cost is due to the complexity of structures of antennas available today.
Back to the early 1990's, a reflector-backed slot-loop antenna was proposed by M. Cai and M. Ito in an article "New Type of Printed Polygonal Loop Antenna; IEE Proceedings-H, Vol. 138, No. 5, Oct. 1991, pp 389-396". The antenna was designed based on the idea of combining a simple polygonal loop antenna and a rectangular slot antenna. Therefore, the antenna as proposed possesses the advantages of polygonal loop and rectangular slot antennas, such as high directivity as well as high tolerance in production. In addition, this antenna is described as having a 24% impedance bandwidth. However, because a rectangular slot is used as a main radiation portion, the radiation is not very efficient. This antenna is not suitable for wider bandwidth applications (such as television) due to its limited bandwidth. Moreover, this type of antenna is limited in the various radiation patterns it provides. In addition, the back feed introduces problems in the manufacturing process.
In view of the various drawbacks associated with current antennas, it would be advantageous to provide an antenna, which mitigates some of these problems to provide a more reliable and efficient antenna design. Therefore, there is a need for an antenna with some of the following characteristics: high gain in order to improve the performance of the existing communication systems such as sensitivity and effective radiation power; increased bandwidth for wider frequency coverage and multiple system applications; configurable for multiple radiation patterns to accommodate different environmental scenarios; a simplified layout for easy manufacture at a high yield and at low cost; and easy installation.